During the fabrication of semiconductor devices, defects are inspected on objects such as wafers and lithographic masks by acquiring images of objects' surfaces and comparing those images to references.
The references may constitute model images, measured images acquired at previous inspection cycles, images simulated based on design data. Several comparison techniques are known, such as die-to-die (D2D), cell-to-cell (C2C), die-to-model (D2M). US Patent Application No. 20130336573 discloses defect detection including patch-to-patch comparisons, and is incorporated herein in its entirety. US Patent Application No. 20140341462 discloses machine learning method and apparatus for inspecting reticles, and is incorporated herein in its entirety.
Lithographic masks are exposed during a lithographic process to radiation thereby forming patterns on a wafer. A lithographic mask error may result in a large number of defective wafers. Therefore—there is a need to rigorously inspect lithographic masks.
A multi-die lithographic mask can be evaluated using die-to-die or cell-to-cell comparison. Such a comparison cannot be applied to a single die lithographic mask.
There is a growing need to provide a system and method for evaluating objects such as, but not limited to, lithographic masks and especially single die lithographic masks.
There is a growing need to improve inspection capabilities by providing systems and methods for evaluating objects such as but not limited to wafers and lithographic masks inspected using several imaging modalities.